Due to other security issues, I set one of my doors to permanently unlock. It's a Precision electrified crash bar. An hour later, smoke was pouring out of it and it was too hot to touch. Facilities tore it open and cut the power wires (I was not available).
My question is, did the crash bar smoke because it's 20+ years old, or did I ask too much of it by keeping it energized in the unlock position?
If the solenoid wasn't rated for 'continuous duty', the burn up wasn't caused by age, but by misuse.
It's a scary thing! I have to ask, what 'security issue' would cause a door to be permanently unlocked?
In general, mechanical override for unlocking (called dogging) allows an exit device to remain unlocked without needing to pass current continually to a solenoid latch retractor.
The badge reader itself on that door failed. So, staff had no way to scan their badge to get into the door until we can get a contractor out to replace it.
The mechanical over ride makes sense. Just don't know if it's something that us, and end user, facility staff could or would do
The badge reader itself on that door failed. So, staff had no way to scan their badge to get into the door until we can get a contractor out to replace it.
That's interesting, and it makes sense why the unlock was needed.
Here's a typical 'dogging' arrangement:
Of note, dogging is not an option on Firedoors (as image notes), because a firedoor must always be positively latched closed to be code compliant.
If the firedoor was 'dogged open', it could blow or flap open and defeat the whole purpose of the firewall!
I don't see that this bar has a hole like that. I've seen it on others.
I am pretty sure that it is a fire door, since it's in a corridor
Your incident could be the result of a 'perfect storm' of code compliance and hardware spec!
The situation really illustrates how complex access control can become.
From what I read, 'continuous duty' latch retraction is often controlled by a motor/gearbox, not a solenoid - primarily to avoid the heat hazard that you experienced! The motorized solution is much lower heat, but is higher priced, sometimes 2X more.
Of note, dogging is not an option on Firedoors (as image notes), because a firedoor must always be positively latched closed to be code compliant.
Though doesn’t electric dogging (integrated with the FAS) allow an exception to the “a firedoor must always be positively latched closed to be code compliant” rule?
Yes, if it can be relieved via a fire-alarm activation, dogging is allowed. But not all facilities with fire walls/ fire doors have alarms (ie: grandfathered buildings), so getting the AHJ to approve a variance may also be needed.
Here's a typical 'dogging' arrangement:
Here’s a slightly cheaper ‘dogging’ retrofit ;)
The Fire Inspector in my county would sh*t a brick if he saw that (assuming firedoor).
The Fire Inspector in my county would sh*t a brick if he saw that...
Actually the zip-tie is made from a special polymer which melts at around 100F ;)
Did anyone check to see what the power supply output was? In my experience with older Von Duprin hardware we would regularly see the voltage regulation on a PS873 power supply get way out of wack. Often over twice the rated voltage output. I would try to find the power supply and see what its output is under load to eliminate that variable.
Was the fire in the crash bar or in the wire transfer, especially if it is a transfer hinge. I have seen the wires in the hinge melt together then cause the crash bar to short out.
Appeared to be from the motor. They said the smoke was coming from the center of the bar.
If there ever is a next time. Just remove the strike plate. Two screws, easy.
Scary situation though.
Which model crash bar was it and how exactly did you “set it to permanently unlock”?
At least some Precision electrified crash hardware has remote dogging via continuous duty solenoids:
Through my S2 access control system. I just set the door lock to 'timed unlock' . I do not know the model number, though I'm confident that it's OLD.
I am confident that the kind folks over at Dormakaba/Precision would love to hear about this. I'd suggest reaching out to their tech support if you haven't already. Even if it's a 20-year old device, letting all the smoke out of a device like that is something I doubt they see or hear very often and would probably like to know more about.
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